The Industrial, Scientific and Medical (ISM) radio bands include portions of the radio spectrum that are reserved internationally for the use of radio frequency (RF) transmissions for industrial, scientific and medical purposes. Generally, there is no regulatory protection from ISM device operation and equipment operating in the ISM bands must tolerate any interference generated by ISM equipment. Although these bands were originally not intended for telecommunications, in recent years the ISM bands have been used for short-range, low power communications systems, such as cordless phones, Bluetooth devices, near field communication (NFC) devices, and wireless computer networks, that use frequencies in the ISM band as well as other frequencies allocated to low power communications.
For example, the IEEE 802.11 Wi-Fi standards identify the channels that may be used for a Wireless Local Area Network (WLAN). The 2.4 GHz ISM band is from 2400 MHz-2500 MHz. There are fourteen channels defined for use by 802.11 Wi-Fi for the 2.4 GHz ISM band. These 802.11 channels span 2402 MHz-2483 MHz. 802.11 Wi-Fi is adapted for use within unlicensed spectrum, which enables users to access the radio spectrum without the need for the regulations and restrictions; however this spectrum is also shared by many other users and is exposed to interference.
Devices using the Bluetooth wireless technology standard also operate in the 2.4 GHz ISM band at 2.4 GHz-2.485 GHz. Bluetooth devices are used in short-range personal area networks. To reduce interference with other protocols that use the 2.4 GHz ISM band, the Bluetooth protocol divides the band into seventy-nine channels and changes channels many times per second. Bluetooth devices may also detect existing signals in the ISM band and attempt to avoid them by negotiating a channel map with other Bluetooth devices.
Long Term Evolution (LTE) cellular networks operate in a number of assigned bands, including the bands 2300 MHz-2400 MHz and 2500 MHz-2690 MHz, which are adjacent to both sides of the ISM band.
The transmissions by each of these systems cause interferences to the other systems' reception. Additionally, intermodulation causes degradation of the LTE transmission links.